Indirect dental restorations are typically fabricated outside of the mouth using a dental impression and/or digital methodologies and may be permanently bonded to a prepared tooth or other dental structure with a dental cement or the like. Such restorations include, for example, veneers, onlays, inlays, bridges, crowns, and many others. Ceramic restorations are particularly desirable, because their color and translucency can mimic natural tooth enamel.
Digital technologies have facilitated the use of ceramics, including, for example, zirconium oxide, in these applications. In one example, such methods include optically scanning the three-dimensional surface of a dentition impression. The resulting captured shape data may be modified to take into account downstream processing effects such as shrinkage. After calculating numerical control data from the shape data, the numerical control data is sent to a milling machine to prepare a ceramic blank fitting the shape data. The resulting ceramic blank is then sintered to provide the finished ceramic restoration.
Because the ceramic material shrinks during sintering, certain sintering supports have been devised with the aim of reducing resistance to the shrinkage occurring in the ceramic restoration, caused by the sintering support. Examples of such sintering supports include aluminum oxide pegs, platinum alloy hangers, and certain swing-type suspension systems. In another example, a bed of ceramic beads has been used as a sintering support upon which the ceramic restoration rests during the sintering. However, in some instances, problems such as poor fit and discoloration of the restoration have been encountered.
There is, therefore, a continuing need for improved sintering processes and materials for preparing indirect dental ceramic restorations.